I understand that you posted the wrong code but a small change in the original will work as (apparently) intended. Specifically, the first '+' should be moved outside the square brackets since "\w", "_", "-" are all in the set you're looking for.

In other words, change ([\w+\_\-]) to ([\w\_\-]+). Better yet, since "_" is included in "\w" and "-" doesn't need to be escaped if it's first or last, you can simplify this to ([\w-]+).